System in a Network Node for Regulating Temperature of Electronic Equipment

ABSTRACT

A system in a radio network node for regulating temperature of electronic equipment comprises the electronic equipment and a heat exchanger unit ( 200 ), comprising an evaporator unit ( 202 ), a condenser unit ( 203 ), and a first pipe ( 204 ). The first pipe ( 204 ) is arranged to connect the evaporator unit ( 202 ) and the condenser unit ( 203 ). A second fluid is flowable from the condenser unit ( 203 ) to the evaporator unit ( 202 ) in the first pipe ( 204 ). Furthermore, the system comprises a heater unit ( 201 ) arranged at the first pipe ( 204 ) and arranged to heat the second fluid in the first pipe ( 204 ) such that flow in the first pipe ( 204 ) is restricted. Furthermore, an arrangement ( 160 ) for restricting flow in a heat exchanger unit is provided.

TECHNICAL FIELD

The present invention relates to a system in a radio network node, moreparticularly, to a system in a radio network node for regulatingtemperature of electronic equipment within the radio network node.Moreover, the present invention relates to an arrangement forrestricting flow in a heat exchanger unit.

BACKGROUND

Generally, a radio communication system of today comprises a radioaccess network and a number of communication devices. The radio accessnetwork is built up of several nodes, in particular, radio basestations. The primary task of a radio base station is to send andreceive information to/from the communication devices within a cellserved by the radio base station. In many cases, the base station is run24 hours a day. Therefore, it is of particular interest and importanceto ensure that the base station is operable predictably and reliably.The radio base station further comprises a cabinet, which comprises anenclosure for housing circuitry, or electronic equipment, for performingdifferent tasks of the radio base station. For example, the circuitrymay comprise a power control unit, a radio unit, comprising a radioamplifier, and a filtering unit for performing corresponding tasks.

Due to low efficiency in the radio amplifier of the radio base station,heat generated in the circuitry of the base station, in particular theradio unit, may not always dissipate naturally to a sufficiently highdegree. Instead, heat is accumulated in the circuitry and temperature ofthe circuitry increases. The increased temperature of the circuitry maydecrease the performance of circuitry within the radio base station,e.g. the circuitry within the radio base station may fail. Consequently,unpredicted interruptions in operation of the base station may occur.This is clearly not desired.

Hence, as is known in the art, systems for cooling of heat generatingequipment within a radio base station have been developed. These systemsare sometimes referred to as climate systems or climate control systemsfor radio base stations.

An example of such a system for cooling of heat generating equipment isdescribed below. The system comprises fans, which are used to circulateair through or over the heat generating equipment and through or overone side of a heat exchanger, i.e. an internal side within theenclosure. Moreover, further fans are used to force ambient air throughor over the other side of the heat exchanger, i.e. an external sidewithin the cabinet. The heat exchanger comprises a refrigerant thatabsorbs heat from air, heated by the electronic equipment, at theinternal side within the enclosure. As a result, a transition fromliquid phase to gas phase of the refrigerant occurs. The portion of theheat exchanger that is located at the internal side within the enclosureis called evaporator. The gas is forced to the external side of the heatexchanger, where it dissipates heat to ambient air. As a result, atransition from gas phase to liquid phase of the refrigerant occurs inthe external side of the heat exchanger. The portion of the heatexchanger that is located on the external side is called condenser. Atthis stage, gravity forces the liquid to flow towards the evaporator.This kind of heat exchanger is generally denoted a thermosiphon.

A disadvantage with this kind of system, which comprises a thermosiphon,is that the electronic equipment may become unnecessary cold during, forexample, cold weather conditions. As a result, performance of theelectronic equipment is impaired.

SUMMARY

It is an object of the present invention to provide a system with a morereliable temperature regulation of the electronic equipment.

According to a first aspect of the invention, the object is achieved bya system in a radio network node for regulating temperature ofelectronic equipment within the radio network node. The system comprisesa closed space comprising a flow generating device and the electronicequipment, wherein the flow generating device is arranged to circulate afirst fluid within the closed space such that heat is transferrablebetween the electronic equipment and the first fluid. The system furthercomprises a heat exchanger unit, comprising an evaporator unit, acondenser unit, and a first and a second pipe. The evaporator unit is atleast partly located within the closed space and the condenser unit isat least partly located outside the closed space. The first and secondpipes are arranged to connect the evaporator unit and the condenserunit, whereby a loop is formed. A second fluid is flowable from thecondenser unit to the evaporator unit in the first pipe and from theevaporator unit to the condenser unit in the second pipe. Furthermore,the system comprises a heater unit arranged at the first pipe andarranged to heat the second fluid in the first pipe such that flow inthe first pipe is restricted, whereby temperature of the electronicequipment is regulated.

According to a second aspect of the present invention, the object isachieved by an arrangement for restricting flow in a heat exchangerunit. The heat exchanger unit comprises an evaporator unit, a condenserunit, and a first and a second pipe. The first and second pipes arearranged to connect the evaporator unit and the condenser unit, wherebya loop is formed. A second fluid is flowable from the condenser unit tothe evaporator unit in the first pipe and from the evaporator unit tothe condenser unit in the second pipe. Furthermore, the system comprisesa heater unit arranged at the first pipe and arranged to heat the secondfluid in the first pipe such that flow in the first pipe is restricted.

An idea of the invention is to reduce flow in the heat exchanger unit,whereby heat transportation to and/or from the electronic equipment viathe first and second fluid is reduced. This is achieved by the systemaccording to appended independent claim 1 and by the arrangementaccording to appended independent claim 5 by means of arranging a heaterunit at the first pipe. In this manner, the system and the arrangementprovide regulation of temperature of the electronic equipment withoutaddition of any movable mechanical parts, such as valves or the like. Asa result, a reliable system and a reliable arrangement are provided.

Advantageously, the heater unit provides for flow regulation of thesecond fluid while maintaining the same level of risk for leakage asbefore introduction of the heater unit.

Moreover, the heater unit maintains the same level of flow resistance inthe heat exchanger as before introduction of the heater unit. In otherwords, the heater unit does not introduce any pressure drop between thecondenser unit and the evaporator unit.

A further advantage with the proposed solution is that heater units arereadily and commercially available at low costs.

It is to be understood that the network node may be a radio base stationor any other kind of node in a (radio) communication system, which nodecomprises heat generating electronic equipment. Examples of other kindsof nodes are transmission nodes, remote subscriber switches (RSS) andnodes with similar functionality.

Further features of, and advantages with, the present invention willbecome apparent when studying the appended claims and the followingdescription. Those skilled in the art realize that different features ofthe present invention may be combined to create embodiments other thanthose described in the following, without departing from the scope ofthe present invention, as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention, including its particular featuresand advantages, will be readily understood from the following detaileddescription and the accompanying drawings, in which:

FIG. 1 shows a schematic block diagram of a system according toembodiments of the present invention, and

FIG. 2 shows a schematic block diagram of an arrangement comprising theheat exchanger unit in the system of FIG. 1.

DETAILED DESCRIPTION

Throughout the following description similar reference numerals havebeen used to denote similar elements, parts, items or features, whenapplicable.

FIG. 1. shows a cross sectional, side view of a system 100 according toembodiments of the present invention. The system 100 in a radio networknode 110 for regulating temperature of electronic equipment 120 withinthe radio network node 110 comprises a closed space 130, comprising aflow generating device 140 and the electronic equipment 120. The flowgenerating device 140 is arranged to circulate, as indicated by arrows141, 142, 143, 144, a first fluid within the closed space 130 such thatheat is transferrable between the electronic equipment 120 and the firstfluid. The arrow 144, in the vicinity of the electronic equipment 120,is dashed to indicate that the flow of the first fluid may pass throughor over the electronic equipment 120. The arrow 142, at the flowgenerating device 140, is dashed to indicate that the flow is passedthrough the flow generating device 140. The system 100 further comprisesa heat exchanger unit 200 arranged to transfer heat from the first fluidwithin the closed space 130 to ambient air outside the closed space 130.Optionally, a flow generating device 150 may be arranged to push or todirect ambient air through or over, as indicated by arrow 149, a portionof the heat exchanger 200 that is located outside the closed space 130.In this manner, excess heat from the electronic equipment 120 may betransported from the electronic equipment 120 to the first fluid withinthe closed space 130, from the first fluid to a second fluid comprisedin and circulated within, as indicated by arrows 146, 147, the heatexchanger 200, and from the second fluid to, for example, ambient air.

Now with reference to FIG. 2, there is illustrated a block diagram of anarrangement 160 comprising the heat exchanger unit 200 in the system 100according to FIG. 1. The heat exchanger unit 200 comprises an evaporatorunit 202, a condenser unit 203, and a first and a second pipe 204, 205.The evaporator unit 202 is at least partly located within the closedspace and the condenser unit 203 is at least partly located outside theclosed space. The first and second pipes 204, 205 are arranged toconnect the evaporator unit 202 and the condenser unit 203, whereby aloop is formed. A second fluid, such as a refrigerant fluid or acoolant, is flowable from the condenser unit 203 to the evaporator unit202 in the first pipe 204 and from the evaporator unit 202 to thecondenser unit 203 in the second pipe 205. The arrangement 160 comprisesa heater unit 201 arranged at the first pipe 204 and arranged to heatthe second fluid in the first pipe 204 such that flow in the first pipe204 is restricted. By restricting the flow in the first pipe 204performance of the heat exchanger unit 200 is decreased. As aconsequence, the temperature of the first fluid within the closed space130 is increased. Hence, also temperature of the electronic equipment120 is increased, i.e. temperature of the electronic equipment 120 isregulated. Since the second fluid in the first pipe 204 has atemperature that is close to saturation point (boiling point) of thesecond fluid, only a small amount of heat is needed in order toevaporate the second fluid. The evaporated second fluid, in gaseousphase, causes a flow in the opposite direction to the flow of condensedsecond fluid, in liquid phase, in the first pipe 204. Consequently, dueto the counteracting flows in gaseous and liquid phase, respectively,speed of flow in the loop is decreased or even completely shut off.

When operating the system 100 of FIG. 1 the following steps areperformed simultaneously or as a sequence, starting with any of thesteps described below. As a first step, as indicated by arrow 211, theevaporator unit 202 evaporates the second fluid. As a result, a firstflow, as indicated by arrow 212, of the second fluid from the evaporatorunit 202 to the condenser unit 203 is generated. Next, the condenserunit 203 condenses, as indicated by arrow 213, the second fluid.Thereby, a second flow, as indicated by arrow 214, of the second fluidfrom the condenser unit 203 to the evaporator unit 202 is generated. Thesecond flow is enhanced by gravitation. In a further step, the heaterunit 201 heats the second fluid in the first pipe 204. Since thetemperature of the second fluid is close to saturation point of thesecond fluid, only a small amount of heat transferred to the secondfluid causes the second fluid to evaporate. As a result, a third flow,as indicated by arrow 215, of the second fluid is generated. In thismanner, the third flow, which is directed in the opposite directioncompared to the flow of the second fluid in liquid phase from thecondenser unit 203 to the evaporator unit 202, reduces the overall flowof the second fluid in the loop. Consequently, the reduced overall flowof the second fluid in the loop reduces the amount of heat transferredbetween the electronic equipment and the second fluid. Hence, forexample, cooling of the electronic equipment is reduced.

It may be noted that the heater unit may, alternatively or additionally,be arranged to heat the first pipe, which in turn heats the second fluidtherein.

As mentioned above, the flow of the second fluid in the heat exchangerunit 200 indirectly affects the amount of heat transferred to and/orfrom the electronic equipment. Thus, in a still further step, the heatermay, optionally, be controlled by a controller (not shown), wherebytemperature of electronic equipment comprised in the radio network nodemay be controlled.

Moreover, in some embodiments of the system according to the presentinvention, the heat exchanger unit 200 comprises a thermosiphon. It ispreferred that resistance of or air pressure difference over thethermosiphon is low. Advantageously, the flow generating device 140 maybe operated at low power, i.e. the system may be energy efficient.However, sometimes undesired flows of ambient air through the heatexchanger (see arrow 149) may cause the heat exchanger to cool theelectronic equipment 120 more than desired. The undesired flows ofambient air are generated by and dependent on external weatherconditions. For example, a windy day may cause undesired cooling of theelectronic equipment 120. The provision of a heater unit 201, asdescribed above, allows for a reduction of (or possibly complete shutoff of) the amount of heat transferred from the electronic equipment120, thereby securing that operation of the electronic equipment 120 isnot impaired.

In embodiments of the system according to the present invention, thecondenser unit 203 is located at least partly above the evaporator unit202. Expressed differently, the evaporator unit 202 and the condenserunit 203 are arranged in relation to each other such that the fluidthanks to gravity is passed from the condenser unit 203 to theevaporator unit 202. As a result, fluid evaporated in the evaporatorunit 202 is allowed to pass upwards and fluid condensed in the condenserunit 203 is allowed to pass downwards, in accordance with commonly knownprinciples of fluid dynamics.

In an example of the system according to embodiments of the presentinvention, the electronic equipment 120 and the flow generating device140 are arranged such that heat is transferrable between the electronicequipment 120 and the first fluid, wherein the flow generating device140 is arranged to circulate the first fluid within the closed space130. More specifically, not shown in a Figure, the flow generatingdevice 140 may be arranged next to and at the same level from ground asthe heat exchanger unit 200 in an upper portion of the enclosed space130. Alternatively, the flow generating device 140 may be arranged nextto and at the same level from ground as the electronic equipment 120 ina lower portion of the enclosed space 130, while the heat exchanger unit200 still is located in an upper portion of the enclosed space 130. Aman skilled in the art may find other alternatives for arranging theelectronic equipment 120 and the flow generating device 140 such thatheat is transferrable between the electronic equipment 120 and the firstfluid.

Even though the invention has been described with reference to specificexemplifying embodiments thereof, many different alterations,modifications and the like will become apparent for those skilled in theart. The described embodiments are therefore not intended to limit thescope of the invention, which is defined by the appended claims.

1-5. (canceled)
 6. A system in a radio network node for regulating thetemperature of electronic equipment within the radio network node, thesystem comprising: a flow generating device enclosed along with theelectronic equipment within a closed space, wherein the flow generatingdevice is configured to circulate a first fluid within the closed spacefor transferring heat between the electronic equipment and the firstfluid, a heat exchanger unit configured to transfer heat between thefirst fluid and a second fluid circulated within the heat exchangerunit, the heat exchanger unit comprising an evaporator unit, a condenserunit, and a first and a second pipe, wherein the evaporator unit is atleast partly located within the closed space, wherein the condenser unitis at least partly located outside the closed space, wherein the firstand second pipes are configured to connect the evaporator unit and thecondenser unit within a loop, wherein the condenser unit is configuredto condense the second fluid into a liquid phase for flow of condensedsecond fluid from the condenser unit to the evaporator unit via thefirst pipe, and wherein the evaporator unit is configured to evaporatethe second fluid into a gaseous phase for flow of evaporated secondfluid from the evaporator unit to the condenser unit via the secondpipe, and a heater unit arranged at the first pipe and configured toheat and at least partially evaporate the second fluid in the first pipeto thereby create in the first pipe a flow of evaporated second fluid,in gaseous phase, in a direction opposite the flow of condensed secondfluid, in liquid phase, wherein the flow of evaporated second fluid inthe first pipe regulates the flow of condensed second fluid in the firstpipe and indirectly regulates the temperature of the electronicequipment.
 7. The system according to claim 6, wherein the second fluidis a refrigerant fluid.
 8. The system according to claim 6, wherein theheat exchanger unit comprises a thermosiphon.
 9. The system according toclaim 6, wherein the network node is a radio base station.
 10. Thesystem according to claim 6, further comprising a controller configuredto control the heater unit and to thereby regulate the extent to whichthe heater unit evaporates the second fluid in the first pipe.
 11. Aheat exchanger unit configured to regulate the temperature of electronicequipment, wherein heat from the electronic equipment is transferred toa first fluid and wherein the heat exchanger unit is configured totransfer heat from the first fluid to a second fluid circulated withinthe heat exchanger unit, the heat exchanger unit comprising: anevaporator unit, a condenser unit, and a first and a second pipe,wherein the first and second pipes are configured to connect theevaporator unit and the condenser unit within a loop, wherein thecondenser unit is configured to condense the second fluid into a liquidphase for flow of condensed second fluid from the condenser unit to theevaporator unit via the first pipe, and wherein the evaporator unit isconfigured to evaporate the second fluid into a gaseous phase for flowof evaporated second fluid from the evaporator unit to the condenserunit via the second pipe, and a heater unit arranged at the first pipeand configured to heat and at least partially evaporate the second fluidin the first pipe to thereby create in the first pipe a flow ofevaporated second fluid, in gaseous phase, in a direction opposite theflow of condensed second fluid, in liquid phase, wherein the flow ofevaporated second fluid in the first pipe regulates the flow ofcondensed second fluid in the first pipe and indirectly regulates thetemperature of the electronic equipment.
 12. The heat exchanger unitaccording to claim 11, wherein the second fluid is a refrigerant fluid.13. The heat exchanger unit according to claim 11, wherein the heatexchanger unit comprises a thermosiphon.
 14. The heat exchanger unitaccording to claim 11, further comprising a controller configured tocontrol the heater unit and to thereby regulate the extent to which theheater unit evaporates the second fluid in the first pipe.